Method and apparatus for casting or injection-molding of cages of cylindrical rolling elements

ABSTRACT

In a method and apparatus for casting or molding cages for rolling elements, two slides are provided for each pocket. The slides have an engaging, inclined surface, and are shaped to permit one of the slides to be removed by initially sliding it along the inclined surface. The other slide may thereby be moved laterally in the formed pocket, and withdrawn from the pocket. Facing slides of adjacent pockets may be joined together, with limited movement possible therein, to form a complete ring serving as a mold member.

This is a division of application Ser. No. 210,217, filed Nov. 25, 1980now U.S. Pat. No. 4,362,687.

This invention relates to a method and apparatus for casting theinjection-molding cages for cylindrical rolling elements. Such cageshave retaining projections for the rolling elements. These projectionsextend both inside and outside the cage along the lateral surfaces ofthe webs which extend between the pockets thereby. The invention employstwo mold slides or cores for each pocket. The slides are retractablefrom the pockets and support one another along an inclined partitionedge when they are in the pockets. The lateral surfaces of the slideshave shapes that are equivalent to the shapes of the lateral surfaces ofthe webs, i.e., within the pockets of the cage.

It is necessary in cages, particularly in the case of cages forcylindrical rolling elements, that retaining projections be provided forperfect radial inward and outward retention of the rolling elements. Theprojections must be provided, both in the bore and on the periphery ofthe cage, in the area of the webs that define circumferential sides ofthe pockets. The projections thus protrude into the pockets. Since theclear width of a pocket, in the region of the retaining projection, issmaller than the clear width in the region of the thickest point of therolling element, the manufacture of such cages from materials that maybe cast or injection molded can only be effected by means of sectionalslides or cores.

In a known method and apparatus for manufacturing such a cage, a slideis divided, for instance, into three parts, in a circumferentialdirection. The outermost slides, in a circumferential direction, areprovided with external surfaces which follow the contour of the lateralsurfaces of the webs, and their internal surfaces are inclined toaccommodate the third slide between them. The third slide also hasinclined lateral surfaces. After the injection molding or casting of thecage, initially the inner, wedge shaped, slide is retracted radiallyoutwards (or inwards), whereupon the outer slides are moved toward oneanother in a circumferential direction, and are then also retractedradially outward or inward. Such an arrangement is disclosed in DE-OSNo. 1,575,532.

This known method and apparatus has the disadvantage that many slidesare needed for each pocket, and that the surfaces of the slides thatcontact other slides, and the guide surfaces for these slides, must beproduced with extreme accuracy. Furthermore, this known method andapparatus may not be used for the manufacture of cages for therelatively thin rolling elements, because the slides then must be sothin walled, that the required stiffness and precision cannot beachieved. Also, the waste resulting from the use of this large number ofslides is very great, so that only a limited number of cages having therequired precision can be produced.

A method and apparatus are also known in which only two slides arerequired for each pocket. Here, one slide is pushed by means ofresilient elements against the other of the slides, which is mounted inan inclined position. In this arrangement the angle of inclination isprecisely equivalent to the angle of inclination of the retainingprojections. After the injection-molding or casting, the slide that isarranged in an inclined position is pulled out obliquely outwards,whereby the other slide flips over to the outside, because of thespring-action, and is thus swung out of the cage pocket. This isdisclosed in DE-OS No. 1,729,327. This design may only be used for cagesin which the width of the pockets (in a circumferential direction) isgreater than the radial height of the pocket, since otherwise the secondslide cannot be swung out.

It is therefore an object of the present invention to provide a methodand apparatus for the manufacture of cages for the retention of rollingelements, from materials that may be cast or injection-molded, and whichpermits the use of relatively brittle materials. The invention also isdirected to the forming of cages with well-shaped retaining projections,and wherein the apparatus has a minimum number of parts. The apparatusis sufficiently stable, even for producing cages for small diametersrolling-elements and has a long life without premature wear of theparts, which wear might impair the precision of the cages.

The method of the invention enables the retraction of the mold slides orcollapsible cores that form the pockets, without an elastic or plasticdeformation of the retaining projections occuring.

In accordance with the invention, an apparatus is provided in which,after the casting or injection-molding of the cage, one mold slide of apocket at a time can be retracted outward, obliquely along the partitionsurface, until it reaches a point at which that surface of the slideforming the farthest protruding lateral surface of the web leaves theoverlap region of the retaining projection. Thereafter this slide isretracted radially further out of the pocket. Simultaneously orsubsequently thereto, the other slide may be retracted along thecorresponding retaining projection, e.g., by a translation movementtransverse of the longitudinal axis of the pockets, or is also oblique.In this fashion, a distortion of the retaining projection is preventedupon removing from the mold, so that the cages may be manufactured forreliable operation even with small rolling-element diameters and out ofrelatively brittle material.

In order that the invention will be more clearly understood, it will nowbe disclosed in greater detail, with reference to the accompanyingdrawings, wherein:

FIG. 1 a partial cross-section of a cage for a radial rolling elementbearing with cylindrical rolling elements;

FIG. 2 a partial cross-section of an apparatus for for the manufactureof the cage according to FIG. 1; and

FIG. 3 shows the various stages of mold-removal of the mold slides orcollapsible cores, wherein the various stages of the mold-removal areillustrated in individual pockets, in a clockwise direction.

FIG. 1 is a partial cross-section of an annular cage having pockets 2distributed about its circumference for receiving cylindrical rollingelements 3. The pockets 2 are separated in the circumferential directionby webs 1. In order to retain cylindrical rolling elements 3 in thepockets 2, the inside and outside surfaces 4 of the webs 1 are providedwith retaining projections 5 and 6, which protrude into the pockets 2.These projections narrow the clear width of the pocket openingssufficiently that the rolling elements cannot fall out of the pockets,once they have been inserted. Due to the narrowing of the pockets 2 inthe region of its inner and outer surfaces, the cage cannot bemanufactured in a simple manner of material that can be cast orinjection-molded, since the cores that form the pocket must be capableof being retracted without damaging or permanently distorting theretaining projections. This risk is particularly great when the cagesare made of brittle material. When the cages are designed for relativelythin rolling elements, these retaining projections are necessarilyrelatively small, so that even a small distortion of the retainingprojections does not provide the absolutely secure retention of therolling elements.

The apparatus shown in FIG. 2 is provided for producing the cageaccording to FIG. 1. It has two mold cores or slides 7 and 8, for theformation of each pocket 2. The slides are in contact with one anotherin the region of pocket 2, along the partition surface 9. This partitionsurface 9 is inclined at an angle α' to the center plane 10 of thepocket 2, i.e., the plane which passes through the center of the pocketand through the center axis of the cage. The angle α' is greater thanthe angle α between tangent 11 to the tip 12 of the projections withinthe pocket, and the center plane 10 of the pocket 2. The partitionsurface 9 of slide 8 is longer, namely by at least the amount "a" (seeFIG. 3), i.e., the base length of retaining projection 5, compared tothe length of the other slide 7. The two facing lateral surfaces 13 and14 of slides 7 and 8 respectively are set back with respect to oneanother, so that a free space 15 is provided between slides 7 and 8.Space 15 is provided for the retraction of slide 7 from pocket 2. Slides7 and 8 of adjacent pockets support one another after insertion, alongtheir outer lateral surfaces 17 and 16 respectively, such that a closed"ring" is produced. This ring thereby fixes the precise position of theslides, without requiring any special additional guide surfaces orsimilar devices for that purpose.

The facing slides 7 and 8 of adjacent pockets are inter-connected by abolt 18, which extends through elongated hole 19 in one of the slides.Upon retracting slide 7 through a distance determined by the dimensionsof elongated hole 19, the slide 8 coupled thereto is carried along withthe slide 7 in an outward direction. In order to enable slide 7 to passthe projection 5 of the pocket without any deformation of the projection5, the limiting edge 7 of the bolt 18 is designed as illustrated to haveplay in relation to the corresponding lateral surface of the respectiveelongated hole 19.

After casting or injection-molding the cage, initially each slide 7 isretracted obliquely outward, along partition surface 9, until itsanterior edge 20 reaches a point that is radially underneath the mostexternal point 12 of retaining projection 5, as shown at (b) in FIG. 3.In order to negotiate this "undercut," partition surface 9 on mold slide8 must be longer by at least the base length "a" of retaining projection5, compared to the corresponding surface on slide 7. Slide 7 is nowretracted outwardly directly in a radial direction, until its lower edge21 reaches a point outside of pocket 2, as shown at (c) in FIG. 3. Thespace 15 between the slides 7 and 8 is required for this purpose. Next,slide 8 is slid laterally or obliquely in the pocket, until its anterioredge 22 reaches a point radially underneath the outermost point 23 ofretaining projection 5 on the right side of the pocket, as seen at (e)in FIG. 3. Next, slide 8 is also retracted outward in a radialdirection, for example to the position shown at (e) in FIG. 3, orcompletely out of the pocket if the dimensions of the slide permit this.In the arrangement shown in (e) of FIG. 3, of course, a further obliquewithdrawal may be employed, whereupon the finished cage is ejected. Thebolt 18 and hole 19 are dimensioned to permit all of the above stepswithout removal of the bolts.

As a modification of the sequence described, after the slide 7 isretracted obliquely, the retraction of slide 8 may be started, while theformer slide continues its retraction.

Although the apparatus described above is designed for the manufactureof cages for radial bearings, it is also possible to provide, on thesame basis, an apparatus for the manufacture of cages for axial bearingsas well as linearly moveable bearings.

What is claimed is:
 1. In an apparatus for casting or injection-moldingcages which have retaining projections for retaining cylindrical rollingelements, the projections being provided on both the inside and outsideof the cage along the lateral surfaces of the webs located between thecage pockets, wherein the width of said pockets is less than theirradial height and, wherein said apparatus has only two mold slides perpocket, the slides being retractable from the pockets and, when in theinserted position, engage one another along an inclined partition edge,the slides having lateral surfaces facing away from one another thathave shapes equivalent to the shape of the corresponding lateralsurfaces of the webs; the improvement wherein said partition surface ofthe two mold slides per pocket is shaped, over part of the length ofeach of the slides for each pocket, to be inclined at an angle α' withrespect to the center plane of the pocket which extends through the axisof the cage, this angle α' being greater than the angle α between thetangent of the retaining projection at the outermost point and saidpocket center-plane, and wherein said two mold slides are mounted to beremovable from the same side of the respective pocket.
 2. The apparatusof claim 1, wherein the inclined partition surface of one slide extendsby at least the base length of retaining projection, as compared to thelength of the partition surface of the respective second mold slide, thefacing lateral surfaces of the mold slides being set back with respectto one another, to form a free space therebetween.
 3. The apparatus ofclaim 2, wherein facing mold slides of adjacent pockets are mounted todirectly support one another.
 4. The apparatus of claim 3, wherein saidfacing slides of adjacent pockets are loosely fastened to one another topermit relative sliding motion in relation to one another withindetermined limits.
 5. The apparatus of claim 4, wherein one of saidfacing slides of adjacent pockets is provided with screws, bolts, pinsor similar devices, which engage elongated holes of the other saidfacing mold slide of adjacent pockets, for sliding and for limiting thesliding of the facing slides of adjacent pocket.
 6. An apparatus formolding or casting an element having webs between a plurality ofadjacent pockets, the width of said pockets being less than their radialheight, said apparatus comprising, for each pocket, a first slide havinga one end side with a shape corresponding to the shape of one side of apocket, the opposite side of said one end being planar and inclined tothe central plane of said pocket between the two lateral sides thereof,and a second slide having one end side planar and engaging the saidplanar end of the said first slide, and an opposite end side shaped toform the other side of the respective pocket, the inclination of saidplanar end sides and the shape of the said opposite end side of thesecond slide, permitting said second slide to be slid out of a formedpocket along said planar end surfaces of the two slides, to a pointpermitting direct removal thereof in the direction of the said centerplane, said first slide being mounted to be removable from the pocket inthe same direction as said second slide.
 7. The apparatus of claim 6,comprising means for slidably joining a first slide for forming eachpocket to the second slide for forming the adjacent pocket.
 8. Theapparatus of claim 7 wherein said joining means comprises an elongatedslot in one of the slidably joined slides, and a bolt in the other ofthe slidably joined slides and extending into the respective slot, therespective slides for forming each pocket, except along the respectiveinclined surfaces, being spaced apart to permit the sliding of therespective first slide out of the pocket of the formed element.
 9. Theapparatus of claim 8 wherein said element is a bearing cage, said centerplane extending through the center of the pocket and the axis of saidcage, the slides extending in one radial direction from the pockets andhaving surfaces defining the respective radial side of the cage.